In wireless communications networks, such as networks that adhere to the known Long-Term Evolution (LTE) standard transmissions over the wireless channel user preselected numerology. The term numerology is used to refer to the parameters used to define the waveform transmission. The numerology parameters include the sub-carrier spacing, the length of a cyclic prefix, the length of an OFDM symbol, the number of symbols contained in a Transmission Time Interval, and the duration of the TTI in milliseconds (ms). LTE networks typically support a 15 kHz sub carrier spacing across all transmission frequencies, with a TTI of 1 ms. It will be understood that a 15 kHz spacing typically results in a symbol rate of 66.7 μs, and that the length of a Cyclic Prefix is 4.69 μs.
For one example, the single subcarrier spacing may be limiting in very high speed mobility scenarios (e.g., 500 Km/h), which may incur high Doppler frequency shift. For another example, the single subcarrier spacing may be limiting in scenarios in which high radio frequency bands, such as 10 GHz bands, are employed, where phase noise may lead to large frequency shift. In such cases, 15 kHz may not be wide enough to accommodate the Doppler impact in frequency domain. On the other hand, low cost devices employing Machine-Type Communications (MTC) or Device to Device (D2D) communications may use narrower frequency bandwidth to enhance coverage and save energy. In such cases, subcarrier spacing can be narrower than that used in networks such as LTE.